External surgical microscopes have been used to provide imaging of surgical fields with high resolution and high magnification. However, these images are limited to being two-dimensional. It is therefore difficult for some surgeons to visualize any depth information of the imaged tissue. It also does not provide any depth perception of the tools surgeons used in the field. Optical Coherence Tomography (OCT) enables imaging of tissue with depth limited to typically 1-3 mm due to the light absorption and scattering property of tissue.